Switching power supply device

ABSTRACT

Provided is a switching power supply device capable of easily realizing multi-phase operation and current balancing with the number of operation phases depending on the amount of load. The switching power supply device includes: a main circuit; a control circuit (2) configured to output a reference pulse signal; an entire current detection circuit CT0 configured to detect an output current of the entire main circuit as an entire current; a plurality of individual current detection circuits CTn provided corresponding to a plurality of power conversion units and configured to detect output currents of respective ones of the plurality of power conversion units as respective individual currents; and a pulse corrector (3) configured to generate individual pulse signals for respective ones of the plurality of power conversion units on the basis of the entire current, the individual currents and the reference pulse signal, and to output, to the plurality of power conversion units, respective ones of the individual pulse signals for the plurality of power conversion units as drive signals for respective switching elements, wherein the pulse corrector (3) determines the number of operation phases N′ for the power conversion units on the basis of the entire current and, to the same number of power conversion units as the determined number of operation phases N′, outputs respective ones of the individual pulse signals.

TECHNICAL FIELD

The present invention relates to a switching power supply device thatconverts an input voltage into an output voltage by using a plurality ofconverter units connected in parallel with each other.

BACKGROUND

In recent years, in association with the increase in output load, therehas been known a multi-phase switching power supply device in which thenumber of operation phases is set to be two or more and the operationphases are driven in respective different phases shifted from eachother, in order to realize large-current and low-ripple operation. Sucha switching power supply device needs to be operated such that a currentsupplied to a load is equally shared by the operation phases. In thisrespect, there has been proposed a technology that detects a currentdeviation for each of the operation phases and adds a compensationsignal for reducing the deviation to zero to a duty command value,thereby operating the device with a current being equally shared by theoperation phases, without causing increase in size or complexity of thedevice (for example, Patent Document 1).

CITATION LIST Patent Literature

Patent Document 1: Japanese Laid-Open Patent Application No. 09-215322

SUMMARY OF INVENTION Technical Problem

However, the prior-art technology requires change of the control circuititself because it performs multi-phase operation on the basis of valuesobtained by adding current compensation values to duty command values,and it accordingly has a problem in that its application to a switchingpower supply device employing a microcomputer or a dedicated analogcontrol IC is difficult. For example, in the case of employing amicrocomputer, calculation of the current compensation for each phaseneeds to be performed within the microcomputer, which requires anexisting control program to be changed to a large extent. Further, whilea plurality of PWM counters need to be used in the microcomputer forperforming the multi-phase operation, there is limitation on the numberof counters. Accordingly, to increase the number of phases, ahigh-performance microcomputer is required, which results in increase incost. In the case of employing a dedicated analog control IC, there is aproblem in that the application circuit usually is almost fixed, and itaccordingly is difficult to incorporate a current correction circuit forcalculating current compensation for each phase and a phase conversioncircuit.

An objective of the present invention is to solve the above-mentionedproblem of the prior-art technology, and accordingly to provide aswitching power supply device that can easily realize multi-phaseoperation and current balancing with the number of operation phasesdepending on the amount of load, without changing the basic portion ofthe control circuit.

Solution to Problem

A switching power supply device of the present invention includes: amain circuit including a plurality of power conversion units each havinga switching element and connected in parallel with each other; a controlcircuit configured to output a reference pulse signal on the basis of anoutput of the entire main circuit; an entire current detection circuitconfigured to detect an output current of the entire main circuit as anentire current; a plurality of individual current detection circuitsprovided corresponding to the plurality of power conversion units andconfigured to detect output currents of respective ones of the pluralityof power conversion units as individual currents; and a pulse correctorconfigured to generate individual pulse signals for respective ones ofthe plurality of power conversion units on the basis of the entirecurrent, the individual currents and the reference pulse signal, and tooutput, to the plurality of power conversion units, respective ones ofthe individual pulse signals for the plurality of power conversion unitsas drive signals for the respective switching elements, wherein thepulse corrector determines the number of operation phases for the powerconversion units depending on the entire current and, to the same numberof power conversion units as the determined number of operation phases,it outputs respective ones of the individual pulse signals.

Advantageous Effects of Invention

According to the present invention, since current correction andmulti-phase operation are enabled by the use of the pulse corrector onthe basis of a gate pulse signal output from the control circuit, thecontrol circuit is not required to have a function of multi-phase(interleave) operation, and by simply adding the pulse corrector, theswitching power supply device can easily be provided with the interleave(multi-phase) function, and there accordingly is achieved an effect ofmaking it possible to easily realize multi-phase operation and currentbalancing with the number of operation phases depending on the amount ofload.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a circuit configuration of a firstexample embodiment of a switching power supply device according to thepresent invention.

FIG. 2 is a waveform diagram showing an example of operation waveform ina pulse corrector shown in FIG. 1.

FIG. 3 is a waveform diagram showing another example of operationwaveform in the pulse corrector shown in FIG. 1.

FIG. 4 is a block diagram showing a circuit configuration of a secondexample embodiment of a switching power supply device according to thepresent invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, with reference to the drawings, example embodiments of thepresent invention will be described in detail. In the following exampleembodiments, an identical reference sign will be assigned toconstituents serving similar functions, and their descriptions will beappropriately omitted.

First Example Embodiment

A switching power supply device 1 of a first example embodiment is amulti-phase DC/DC converter. Referring to FIG. 1, the switching powersupply device 1 includes a control circuit 2, a pulse corrector 3, anentire current detection circuit CT₀, and N-number of converter unitsCH₁ to CH_(N) collectively corresponding to a main circuit.

In the switching power supply device 1, a power supply V_(in) and a loadL are connected on the input and output sides, respectively. Between thepower supply V_(in) and the load L, the N-number of converter units CH₁to CH_(N) are provided in parallel connection with each other and aredriven as operation phases for first to N-th phases, respectively.

The N-number of converter units CH₁ to CH_(N) are power conversion unitseach including a switching element that is on/off controlled by a pulsesignal. The N-number of converter units CH₁ to CH_(N) have the sameconfiguration. Accordingly, assuming n to represent natural numbers from1 to N, detail description will be given of a converter unit CH_(n). Theconverter unit CH_(n) includes a reactor S_(n), a diode D_(n), aswitching element Q_(n), a capacitor C_(n) and an individual currentdetection circuit CT_(n), thereby constituting a non-isolated step-upchopper circuit. While a non-isolated step-up chopper circuit is thustaken as an example of the converter unit CH_(n) in the present exampleembodiment, the converter unit CH_(n) may be a PWM control converterother than a step-up chopper circuit (a step-down chopper circuit, astep-up/step-down chopper circuit and the like), and may also be anisolated DC/DC converter.

A series circuit is formed by the reactor S_(n) and the diode D_(n), andone end of the reactor S_(n) and the cathode of the diode D_(n), in theseries circuit, are coupled to the power supply V_(in) and the load L,respectively. The capacitor C_(n) is coupled between the load L and aconnection point between the cathode of the diode D_(n) and a groundterminal, and in parallel with the load L on the output side.

In the present example embodiment, the switching element Q_(n) isconstituted by a MOSFET. Of the switching element Q_(n), the drain iscoupled to a connection point between the reactor S_(n) and the diodeD_(n), and the source is coupled to the ground terminal. Accordingly,switching operation of the switching element Q_(n) is controlled by adrive signal applied to the gate, and a voltage of the power supplyV_(in) is thereby boosted and supplied to the load L.

The converter unit CH_(n) further includes an abnormal operationdetector 11 _(n). On detecting an operational abnormality in theconverter unit CH_(n), such as overheat, short circuit and failure, theabnormal operation detector 11 _(n) outputs an operational abnormalitysignal to the pulse corrector 3.

The individual current detection circuit CT_(n) detects a currentflowing through the reactor S_(n), that is, an output current of theconverter unit CH_(n) (for example, an average value over one cycle ofthe gate pulse signal, T_(s)). The individual current detection circuitCT_(n) is constituted by, for example, a current transformer or a senseresistor.

The entire current detection circuit CT₀ detects an input current (forexample, an average value over one cycle of the gate pulse signal,T_(s)) that is input to the entire main circuit (converter units CH₁ toCH_(N)) from the power supply V_(in). An input current detected by theentire current detection circuit CT₀ represents a current input to theentire main circuit (converter units CH₁ to CH_(N)) that is equivalentto a sum of input currents respectively flowing through the converterunits CH₁ to CH_(N). The entire current detection circuit CT₀ isconstituted by, for example, a current transformer or a sense resistor.

The control circuit 2 is a circuit configured to generate a gate pulsesignal for on/off controlling the switching element Q_(n) of theconverter unit CH_(n). The control circuit 2 outputs, to the pulsecorrector 3, the gate pulse signal with its duty ratio (pulse width)being controlled to make an output voltage of the entire main circuit(converter units CH₁ to CH_(N)) be a target value.

Subsequently, based on the gate pulse signal input from the controlcircuit 2, the pulse corrector 3 generates drive signals by correctingthe gate pulse signal in a manner to equalize input currents to theconverter units CH₁ to CH_(N) and adjusting phases of the drive signalsfor multi*phase operation, thereby on/off controlling the switchingelements Q₁ to Q_(N). Accordingly, since the pulse corrector 3 thusimplements multi*phase operation and current balance, what the controlcircuit 2 needs to have is only a function of controlling a single-phaseconverter, and the control circuit 2 does not need to support themulti-phase operation.

The pulse corrector 3 is constituted by a field programmable gate array(FPGA), which functions as a divider 4, drive signal generation units 5₁ to 5 _(N), and a phase control unit 10.

The divider 4 divides an input current detected by the entire currentdetection circuit CT₀ by N′ representing the number of operation phases(N′ is a natural number equal to or smaller than N), thereby calculatingan average current, and outputs the calculated average current to eachof the drive signal generation units 5 ₁ to 5 _(N).

The drive signal generation units 5 ₁ to 5 _(N) have the sameconfiguration. Therefore, assuming n to represent natural numbers from 1to N, detail description will be given of a drive signal generation unit5 _(n) below. The drive signal generation unit 5 _(n) includes a currentdeviation calculator 6 _(n), a compensator 7 _(n), a duty adder 8 _(n)and a phase shifter 9 _(n).

The current deviation calculator 6 _(n) is a subtractor that calculatesa difference between the average current input from the divider 4 and anoutput current of the converter unit CH_(n) detected by the individualcurrent detection circuit CT_(n), as a current deviation.

The compensator 7 _(n) determines a compensatory duty value ΔD_(n) forcompensating for the current deviation calculated by the currentdeviation calculator 6 _(n). Here, for the compensator 7 _(n), aproportional controller (P controller), a proportional-integralcontroller (PI controller), a proportional-integral-differentialcontroller (PID controller) or the like may be used.

The duty adder 8 _(n) generates a drive signal having a gate pulse widthof D+ΔD_(n) that is obtained by adding the compensatory duty valueΔD_(n) determined by the compensator 7 _(n) to a duty value (pulsewidth) D of the gate pulse signal input from the control circuit 2.Accordingly, the generated drive signal becomes the one whose duty valuehas been corrected from that of the gate pulse signal in a direction tomake an output current of the converter unit CH_(n) become closer to theaverage current input from the divider 4.

Assuming a period of the gate pulse signal output from the controlcircuit 2 to be T_(s), the phase shifter 9 _(n) delays the drive signalgenerated by the duty adder 8 _(n) according to a phase angle commandfrom the phase control unit 10, and make the delayed drive signal beoutput to the converter unit CH_(n).

On the basis of an operational abnormality signal input from theconverter units CH₁ to CH_(N), the phase control unit 10 determines anyconverter unit CH_(n) corresponding to the detected operationalabnormality to be an abnormal phase, and recognizes any converter unitCH_(n) in normal operation as a normal phase. Then, the phase controlunit 10 determines the number of operation phases N′ on the basis of acurrent flowing through the entire main circuit (converter units CH₁ toCH_(N)) (an input current detected by the entire current detectioncircuit CT₀), and determines N′-number of operation phases to operate,from among the normal phases excluding the abnormal phases.

The phase control unit 10 reduces the number of operation phases N′ whenthe input current detected by the entire current detection circuit CT₀is small, that is, when the load L is light, while it increases thenumber of operation phases N′ when the input current detected by theentire current detection circuit CT₀ is large, that is, when the load Lis heavy. Thereby, the number of operation phases driven in a light loadstate can be reduced, and switching loss of the switching elements Q_(n)accordingly can be reduced. As a result, it becomes possible to increasethe power conversion efficiency in a light load state.

Further, the phase control unit 10 determines the number of operationphases N′ such that an output current of each of the operation phases beequal to or larger than a specified value. Thereby, the output currentscan be limited so as to prevent significant decrease in the efficiency.

The phase control unit 10 causes the phase shifters 9, of the phases nothaving been included in the N′-number of operation phases to suspendoutputting a drive signal, and it outputs commands for phase anglessequentially varied at an interval of 360°/N′ to the phase shifters 9_(n) of the phases having been included in the N′-number of operationphases. This makes drive signals of the operation phases be output atphase angles sequentially varied at an interval of 360°/N′,respectively.

Further, the phase control unit 10 outputs the number of operationphases N′ to the control circuit 2. Based on the number of operationphases N′, the control circuit 2 determines a control gain of the entiremain circuit (converter units CH₁ to CH_(N)). Specifically, since atransfer function varies depending on the number of operation phases todrive, the control circuit 2 decreases the control gain with decreasingthe number of operation phases N′, according to the number of operationphases N′. It thereby becomes possible to control the switching powersupply device 1 with an optimum control gain regardless of the number ofoperation phases to drive.

Next, with reference to FIG. 2, a method of current correction andmulti-phase generation performed in the pulse corrector 3 will bedescribed in detail. In an example shown in FIG. 2, it is assumed that afirst to N′-th phases have been determined as N′-number of operationphases by the phase control unit 10.

In the pulse corrector 3, the duty adder 8 _(n) of the drive signalgeneration unit 5 _(n) measures a time (pulse width) from the risingedge to the falling edge of a gate pulse signal that is input from thecontrol circuit 2 at a time t₀, as a duty value Dt₀. Here, a periodT_(s) of the gate pulse signal output from the control circuit 2 is tobe a switching period of the converter unit CH_(n).

In parallel with the measurement of the duty value Dt₀, calculation of acurrent deviation by the current deviation calculator 6 _(n) anddetermination of a compensatory duty value ΔD_(n)t₀ by the duty adder 8_(n) are performed.

Then, the duty adder 8 _(n) generates a drive signal having a gate pulsewidth Dt₀+ΔD_(n)t₀ obtained by adding the compensatory duty valueΔD_(n)t₀ determined by the compensator 7 _(n) to the measured duty valueDt₀. Accordingly, gate pulse widths of drive signals for respective onesof the operation phases corresponding to the first to N′-th phases,which are Dt₀+ΔD₁t₀, Dt₀+ΔD₂t₀, . . . , Dt₀+ΔD_(N)t₀, respectively, aredetermined.

Next, the phase shifter 9 _(n) makes the drive signal generated by theduty adder 8 _(n) be output to the converter unit CH_(n), at a timedelayed by T_(s)×(n-1)/N′ from a time t₁ at which the next gate pulsesignal from the control circuit 2 rises. Accordingly, to the converterunit CH₁, a pulse having the gate pulse width Dt₀+ΔD₁t₀ that is to riseat the time t₁ is output as a gate signal for the first phase. Then, tothe converter unit CH₂, a pulse having the gate pulse width Dt₀+ΔD₂t₀that is to rise delaying from the drive signal for the first phase by atime T_(s)/N′ corresponding to a phase of 360°/N′ is output as a drivesignal for the second phase. Similarly, to the converter units CH₂ toCH_(N), drive signals for the third to N′-th phases generated by theduty adder 8 _(n) with their phases being varied sequentially at theinterval T_(s)/N′ are output, respectively.

Then, similar current correction and multi-phase generation areperformed also on a gate pulse signal input at or after the time t₁ tothe pulse corrector 3 from the control circuit 2, and thus generatedsignals are output in a subsequent switching cycle at or after a timet₂.

As has been described above, in the first example embodiment, a gatepulse signal output from the control circuit 2 is input to the pulsecorrector 3, calculation for current correction and phase shiftoperation are performed in the pulse corrector 3, and thereby drivesignals for respective ones of the N′-number of converter units CH₁ toCN_(N′) are output. As a result, even using a microcomputer or adedicated analog control IC for a single-phase switching power supplydevice, it easily becomes possible, by simply adding the pulse corrector3, to realize multi-phase operation and current balancing with thenumber of operation phases depending on the amount of load.

While the first example embodiment has been described to be configuredto execute the multi-phase operation and current balancing with acontrol delay corresponding to one switching cycle, it may be configuredto execute the multi-phase operation and current balancing withoutcausing the control delay. In the latter case, as shown in FIG. 3, inthe pulse corrector 3, the drive signal generation unit 5 ₁ for thefirst phase does not perform calculation of the compensatory duty valueΔD₁, and accordingly outputs a gate pulse signal output from the controlcircuit 2 with no change, as a drive signal for the converter unit CH₁.Then, in the driving signal generation units 5 ₂ to 5 _(N′) for thesecond to N′-th phases, calculation of the respective compensatory dutyvalues ΔD₂ to ΔD_(N′) is performed, thereby executing the currentbalancing.

Referring to FIG. 3, when a gate pulse signal is input from the controlcircuit 2 at a time t₀, the phase shifter 9 ₁ of the drive signalgeneration unit 5 ₁ causes a drive signal for the first phase, which isto be output to the converter unit CH₁, to rise at the time t₀, and inparallel with that, compensatory duty values ΔD_(n)t₀ are calculated inthe drive signal generation units 5 ₂ to 5 _(N′).

Subsequently, the phase shifter 9 ₂ of the drive signal generation unit5 ₂ causes a drive signal for the second phase to rise after elapse of atime interval T_(s)/N′ since the rising of the drive signal for thefirst phase. Then, also the phase shifters 9 ₃ to 9 _(N′) of the drivesignal generation units 5 ₃ to 5 _(N′) successively cause drive signalsfor the second to N′-th phases, respectively, to rise at the sameintervals.

Next, the phase shifter 9 ₁ of the drive signal generation unit 5 ₁causes the drive signal of the first phase to fall simultaneously withfalling of the gate pulse signal at a time t₀+DT₀. In the drive signalgeneration units 5 ₂ to 5 _(N′), immediately on determination of theduty value DT₀ of the gate pulse signal output from the control circuit2, the duty value Dt₀ is added to each of the compensatory duty valuesΔD_(n)t₀ calculated in advance, thereby determining gate pulse widthsDT₀+ΔD_(n)t₀ of drive signals for the respective first to N′-th phases,and the drive signals of the second to N′-th phases are caused to fallaccording to thus determined gate pulse widths DT₀+ΔD_(n)t₀,respectively.

Then, similar current correction and multi-phase generation areperformed also on a gate pulse signal input at or after the time t₁ tothe pulse corrector 3 from the control circuit 2, and thus generateddrive signals are output within the same switching cycle (as the gatepulse signal).

As a result, it becomes possible to realize multi-phase operation andcurrent balancing without causing control delay. In the present case,while current correction for current balancing comes not to be performedon the first operation phase, it is performed in operation of theremaining operation phases, and accordingly, also the first operationphase automatically comes to contribute to the current balancing.

Second Example Embodiment

A switching power supply device 1 a according to a second exampleembodiment is a multi-phase inverter. Referring to FIG. 4, the switchingpower supply device 1 a includes a control circuit 2, a pulse corrector3, an entire current detection circuit CT₀, and N-number of inverterunits INV₁ to INV_(N) collectively corresponding to a main circuit.Hereafter, description of similar configurations to that of the firstexample embodiment will be appropriately omitted.

In the switching power supply device 1 a, a power supply V_(in) and aload L are connected on the input and output sides, respectively.Between the power supply V_(in) and the load L, the N-number of inverterunits INV₁ to INV_(N) are provided in parallel connection with eachother and are driven as operation phases for first to N-th phases,respectively.

The N-number of inverter units INV₁ to INV_(N) are power conversionunits each including a switching element that is on/off controlled by apulse signal. The N-number of inverter units INV₁ to INV_(N)have thesame configuration. Accordingly, assuming n to represent natural numbersfrom 1 to N, detail description will be given of an inverter unitINV_(n). The inverter unit INV_(n) includes a capacitor C_(n), aninversion buffer NOT_(n), a reactor S_(n), four switching elementsQ_(n-1) to Q_(n-4), and an individual current detection circuit CT_(n),thereby constituting a full-bridge single-phase inverter.

The capacitor C_(n) is connected in parallel with the power supplyV_(in).

In the present example embodiment, the four switching elements Q_(n-1)to Q_(n-4) are each constituted by a MOSFET. Between the positive andnegative terminals of the capacitor C_(n), a series circuit composed ofthe switching elements Q_(n-1) and Q_(n-2) is connected, and also is aseries circuit composed of the switching elements Q_(n-3) and Q_(n-4).

A connection point between the switching elements Q_(n-1) and Q_(n-2) iscoupled to one end of the load L via the reactor S_(n), and a connectionpoint between the switching elements Q_(n-3) and Q_(n-4) is coupled tothe other end of the load L. Between the both ends of the load L, acapacitor C₀ functioning as a filter circuit for removing high frequencycomponents in combination with the reactor S_(n) of the inverter unitINV_(n) is connected.

A drive signal from the pulse corrector 3 is input to the gates of theswitching elements Q_(n-1) and Q_(n-4) directly, and to the gates of theswitching elements Q_(n-2) and Q_(n-3) via the inversion buffer NOT_(n).Thereby, on/off of the switching elements Q_(n-1) to Q_(n-4) is switchedby the drive signal, and conversion of a DC voltage into a desired ACvoltage is thereby performed.

In the second example embodiment, the individual current detectioncircuit CT_(n) detects a current flowing through the reactor S_(n), thatis, an output current of the inverter unit INV_(n). The individualcurrent detection circuit CT_(n) is constituted by, for example, acurrent transformer or a sense resistor. In the second exampleembodiment, the current deviation calculator 6 _(n) of the pulsecorrector 3 calculates, as a current deviation, a difference between anaverage current input from the divider 4 and the output current of theinverter unit INV_(n) detected by the individual current detectioncircuit CT_(n) (for example, an average value over one cycle of the gatepulse signal, T_(s)).

In the second example embodiment, the entire current detection circuitCT₀ detects an output current that is output from the entire maincircuit (inverter units INV₁ to INV_(N)). The output current detected bythe entire current detection circuit CT₀ represents an entire outputcurrent of the main circuit (inverter units INV₁ to INV_(N)) that isequivalent to a sum of output currents flowing through the respectiveinverter units INV₁ to INV_(N). The entire current detection circuit CT₀is constituted by, for example, a current transformer or a senseresistor. In the second example embodiment, the divider 4 of the pulsecorrector 3 calculates an average current by dividing the output currentdetected by the total current detection circuit CT₀ (for example, anaverage value over one cycle of the gate pulse signal, T_(s)) by thenumber of operation phases N, and outputs thus calculated averagecurrent to each of the drive signal generation units 5 ₁ to 5 _(n).

Thus, in the second example embodiment, the gate pulse signal outputfrom the control circuit 2 is input to the pulse corrector 3,calculation for current correction and phase shift operation areperformed in the pulse corrector 3, and thereby drive signals forrespective ones of the N-number of inverter units INV₁ to INV_(N) areoutput. As a result, even using a microcomputer or a dedicated analogcontrol IC for a single-phase switching power supply device, it easilybecomes possible, by simply adding the pulse corrector 3, to realizemulti-phase operation and current balancing.

As has been described above, according to the present exampleembodiments, the switching power supply devices include: a main circuitconstituted by a plurality of power conversion units (converter unitsCH_(n) or inverter units INV_(n)) each having a switching device(switching device Q_(n) or switching devices Q_(n-1) to Q_(n-4)) andconnected in parallel with each other; a control circuit 2 configured tooutput a reference pulse signal on the basis of an output of the entiremain circuit; an entire current detection circuit CT₀ configured todetect an output current of the entire main circuit as an entirecurrent; a plurality of individual current detection circuits CT_(n)provided corresponding to the plurality of power conversion units andconfigured to detect output currents of respective ones of the pluralityof power conversion units as individual currents; and a pulse corrector3 configured to generate individual pulse signals for respective ones ofthe plurality of power conversion units, on the basis of the entirecurrent, the individual currents and the reference pulse signal, and tooutput, to the plurality of power conversion units, respective ones ofthe individual pulse signals for the plurality of power conversion unitsas drive signals for the respective switching elements, wherein thepulse corrector 3 determines the number of operation phases N′ for thepower conversion units on the basis of the entire current and, to thesame number of power conversion units as the determined number ofoperation phases N′, outputs respective ones of the individual pulsesignals. Employing this configuration, multi-phase operation and currentbalancing can be performed by the use of the pulse corrector 3 with thenumber of operation phases depending on the amount of load, on the basisof the gate pulse signal output from the control circuit 2, accordinglythe control circuit 2 does not need to have a function of multi-phaseoperation, and the main circuit can be efficiently operated in amulti-phase manner by simply adding the pulse corrector 3.

Further, according to the present example embodiments, the individualpulse signals for respective ones of the same number of power conversionunits as the number of operation phases N′ are generated by correcting aduty value of the reference pulse signal such that individual currentsof respective ones of the N′-number of power conversion units each be avalue obtained by dividing the entire current by the number of operationphases N′. Employing this configuration, current balancing among theplurality of power converter units constituting the main circuit can berealized by simply adding the pulse corrector 3.

Further, according to the present example embodiments, the pulsecorrector 3 makes the plurality of power conversion units operate in amulti-phase manner. Employing this configuration, an interleave(multi-phase) function can be provided by simply adding the pulsecorrector 3.

Further, according to the present example embodiments, the pulsecorrector 3 outputs the reference pulse signal with no change to anoperation phase corresponding to the first phase, as a drive signal forits switching element, and outputs the generated individual pulsesignals after shifting their phase angles with reference to thereference pulse signal by amounts sequentially increasing at constantintervals, to respective operation phases corresponding to phases otherthan the first phase. Employing this configuration, a duty value D ofthe gate pulse signal determined at a time of outputting the drivesignal for the first phase can be reflected in the second and subsequentphases, and accordingly multi-phase operation and current balancing canbe performed without causing control delay.

Further, according to the present example embodiments, the pulsecorrector 3 outputs the number of operation phases N′ to the controlcircuit 2, and the control circuit 2 changes either or both of a controlgain of the entire main circuit and a threshold value of overloaddetection, on the basis of the number of operation phases N′. Employingthis configuration, safe operation with an optimum control gain furtherbecomes possible.

Further, according to the present example embodiments, the pulsecorrector 3 determines the number of operation phases N′ such that eachof the output currents be equal to or larger than a specified thresholdvalue. Employing this configuration, the output currents can be limitedso as to prevent decrease in the efficiency.

Further, according to the present example embodiments, abnormaloperation detection units 11 ₁ to 11 _(N) configured to detect anabnormal operation in respective ones of the plurality of powerconversion units are provided, and the pulse corrector 3 determines anypower conversion unit on which an abnormal operation has been detectedto be an abnormal phase and suspend outputting an individual pulsesignal for the abnormal phase, and also determines any power conversionunit on which no abnormal operation has been detected to be a normalphase and generates individual pulse signals for the normal phases bycorrecting a duty value of the reference pulse signal in a manner toequalize individual currents of the respective normal phases. Employingthis configuration, even when some of the power converter unitsconstituting the circuit cannot be used because of its operationalabnormality, operation using the remaining normally-operating powerconverter units can be performed with their phase angles kept beingsequentially varied at constant intervals and their current balancebeing maintained. Additionally, since the operation is performed byexcluding an abnormal power converter, redundant operation becomespossible.

Furthermore, according to the present example embodiments, the pulsecorrector 3 outputs the number of normal phases to the control circuit2, and the control circuit 2 changes either or both of a control gain ofthe entire main circuit and a threshold value of overload detection, onthe basis of the number of normal phases. Employing this configuration,safe operation with an optimum control gain further becomes possible.

While the present invention has been described above with reference tothe specific example embodiments, it is obvious that the exampleembodiments are merely examples and may be implemented with any changesor modifications within a range not departing from the spirit of thepresent invention.

REFERENCE SIGNS LIST

1, 1 a switching power supply device

V_(in) power supply

CHto CH_(N) converter unit

S₁ to S_(N) reactor

D₁ to D_(N) diode

Q₁ to Q_(N), (Q₁₋₁ to Q₁₋₄) to (Q_(N-1) to Q_(N-4)) switching element

C₀, C₁ to C_(N) capacitor

CT₁ entire current detection circuit

CT₁ to CT_(N) individual current detection circuit

INV₁ to INV_(N) inverter unit

NOT₁-NOT_(N) inversion buffer

L load

2 control circuit

3 pulse corrector

4 divider

5 ₁ to 5 _(N) drive signal generation unit

6 ₁ to 6 _(N) current deviation calculator

7 ₁ to 7 _(N) compensator

8 ₁ to 8 _(N) duty adder

9 ₁ to 9 _(N) phase shifter

10 phase control unit

11 ₁ to 11 _(N) abnormal operation detection unit

1. A switching power supply device comprising: a main circuit includinga plurality of power conversion units each having a switching elementand connected in parallel with each other; a control circuit configuredto output a reference pulse signal on the basis of an output of theentire main circuit; an entire current detection circuit configured todetect an output current of the entire main circuit as an entirecurrent; a plurality of individual current detection circuits providedcorresponding to the plurality of power conversion units and configuredto detect output currents of respective ones of the plurality of powerconversion units as individual currents; and a pulse correctorconfigured to generate individual pulse signals for respective ones ofthe plurality of power conversion units on the basis of the entirecurrent, the individual currents and the reference pulse signal, and tooutput, to the plurality of power conversion units, respective ones ofthe individual pulse signals for the plurality of power conversion unitsas drive signals for the respective switching elements, wherein thepulse corrector determines the number of operation phases for the powerconversion units on the basis of the entire current and, to the samenumber of power conversion units as the determined number of operationphases, outputs respective ones of the individual pulse signals.
 2. Theswitching power supply device according to claim 1, wherein the pulsecorrector generates the individual pulse signals for respective ones ofthe same number of power conversion units as the number of operationphases by correcting a duty value of the reference pulse signal suchthat the individual currents of respective ones of the same number ofpower conversion units as the number of operation phases be equal to avalue obtained by dividing the entire current by the number of operationphases.
 3. The switching power supply device according to claim 1,wherein the pulse corrector causes the plurality of power conversionunits to operate in a multi-phase manner.
 4. The switching power supplydevice according to claim 1, wherein the pulse corrector outputs thenumber of operation phases to the control circuit, and wherein, on thebasis of the number of operation phases, the control circuit changes acontrol gain of the entire main circuit.
 5. The switching power supplydevice according to claim 1, wherein the pulse corrector determines thenumber of operation phases such that each output current be equal to orlarger than a specified threshold value.
 6. The switching power supplydevice according to claim 1, wherein abnormal operation detection unitsconfigured to detect an abnormal operation in respective ones of theplurality of power conversion units are provided, and wherein the pulsecorrector determines any power conversion unit on which an abnormaloperation has been detected to be an abnormal phase and suspendoutputting the individual pulse signal for the abnormal phase, and alsodetermines any power conversion unit on which no abnormal operation hasbeen detected to be a normal phase and generates the individual pulsesignals for the normal phases by correcting a duty value of thereference pulse signal in a manner to equalize the individual currentsof the respective normal phases.
 7. The switching power supply deviceaccording to claim 6, wherein the pulse corrector outputs the number ofnormal phases to the control circuit, and wherein, on the basis of thenumber of the normal phases, the control circuit changes either or bothof a control gain of the entire main circuit and a threshold value ofoverload detection.